The present invention relates to a steering system for a motorized vehicle with particular emphasis on an electronic steering control for a material handling vehicle, such as fork lift truck.
It is desirable to increase the sensitivity of the steering of a motorized vehicle at low vehicular speeds in order to provide better maneuverability and parking control. At higher speeds the steering sensitivity should be decreased, since large displacements can result from small corrections. One of the best ways to influence the steering sensitivity is to change the steering ratio (i.e., the number of turns from lock-to-lock of the steering wheel or column).
It is further desirable to modify the steering sensitivity utilizing electronic rather than mechanical controls. An electronic steering control system has greater flexibility than a mechanical control system, and is lower in cost. For example, a mechanical control may require replacing or adjusting mechanical gearing, while an electronic system using a microprocessor-based control can be easily modified by changing programming parameters.
Electronic steering control is particularly useful for material handling vehicles, such as fork lift trucks. Such vehicles generally have integrally functioning drive and steering motors. Where the drive and steering functions are united in a common control system, a microprocessor control is an extremely flexible means of providing adjustments and control modifications.